Fan modules such as cooling fan modules are generally used to cool the engine in motor vehicles. Generally a fan module consists of a fan, a motor located at the centre of the fan to drive the fan, and a frame which comprises assembly struts for fixing the motor. Further, the fan of a cooling fan module is designed to produce an air flow with which the heat generated by the engine is removed.
As a fan of the fan module, in particular cooling fan module, a forward sweep fan or a back sweep fan are commonly used. Comparing with a forward sweep fan, a back sweep fan of a cooling fan module of a vehicle has good efficiency over a wider operating range and higher pressure rise at high flow rate, which is needed, when vehicle is under trailer towing condition at 50 to 60 mile per hour speed or 80.47 km/h to 96.56 km/h when a heat rejection rate from the engine of the vehicle is very high. But in general back sweep fan creates more noise than comparable forward sweep fan.
EP 0 500 782 B1 describes a fan comprising multi-sweep blades with abrupt sweep transition. According to EP 0 500 782 B1 the blades are rearward swept inner blades and are formed with a very high forward sweep at the tip.